Usually, silver halide photography includes the exposure stage wherein silver halide is exposed to light to form a latent image. The latent image is developed during photographic processing to form a visible image. Originally, silver halide is sensitive to light only in the spectrum region of blue light. Accordingly, the use of spectral sensitizing dyes is demanded to enlarge the sensitive wavelength region of silver halide to a longer wavelength side.
Silver halide is removed from color photographic materials by photographic processing in the case of processing color photographic materials. In the case of black-and-white photographic materials, unexposed silver halide is removed. In both cases, it is desirable that sensitizing dyes are also removed. Sensitizing dyes left behind without being removed are liable to cause a problem with regard to the formation of residual color, and hence the sensitizing dyes left behind have an adverse effect on images formed on the photographic materials. The problem of residual color grows more and more serious when the use of tabular grain emulsions and high chloride emulsions is increased. Tabular grains contained in the tabular grain emulsions have a large surface area per mol of silver and hence the addition amount of the sensitizing dyes in the grains is high. Accordingly, the residual color becomes high. Grains contained in the high chloride emulsions require the use of sensitizing dyes having enhanced absorptivity to silver halide, and the high chloride grains are often subjected to rapid processing. Accordingly, there is a possibility that the problem of residual color becomes serious.
Most of photographic films which require sensitivity to green light must be highly sensitive to light in the spectrum region of intermediate green light in the wavelength range of 540 to 555 nm (the highest sensitivity range to human eyes) for achieving sufficient sensitivity, color analysis and color reproduction. Benzimidazolocarbocyanine, oxacarbocyanine and benzimidazolooxacarbocyanine dyes are conventional spectral sensitizing dyes which absorb light in the spectrum region of green light. These dyes are disclosed in, for example, Abbott et al's U.S. Pat. Nos. 4,425,425 and 4,425,426 (reexamined No. 907), Ukai et al's U.S. Pat. No. 4,510,235, Yoshida et al's U.S. Pat. No. 4,801,526 and Ikeda et al's U.S. Pat. No. 4,837,140.
Benzimidazolocarbocyanine dyes are very effective in utilizing light energy and are highly basic. Accordingly, the dyes can be protonated and removed in processing using acidic solutions. Accordingly, residual stain is reduced. These dyes highly function as J-aggregate on the surfaces of silver halide grains. However, the benzimidazolocarbocyanine aggregates generally absorb light in the spectrum region of green light having a long wavelength of 560 to 590 nm. Accordingly, another types of dyes such as oxacarbocyanine dyes or benzimidazolooxacarbocyanine dyes must be conventionally used to conduct sensitization in the region of intermediate green light. However, since these dyes are lowly basic, the dyes are liable to be left behind at a high level which is unacceptable after processing.